1. Field of the Invention
The present invention relates to a system for and a method of selecting a pneumatic device, and a recording medium, and more particularly to a system for and a method of selecting an optimum pneumatic device which satisfies specified conditions, and a recording medium which stores a program for selecting such a pneumatic device.
2. Description of the Related Art
In order to construct a pneumatic system, i.e., a terminal system including components from a directional control valve to an air cylinder, which is specified by a user, there has been devised a slide rule for designing a pneumatic pressure control system, as disclosed in Japanese patent publication No. 53-21320.
The disclosed slide rule has fixed and slidable scales marked on face and back sides of the slide rule with graduations to satisfy a formula for determining a stroke time, a formula for determining a cylinder output, a formula for determining an amount of air consumed by the cylinder and a tube connected thereto, and other formulas. In combination with cursor operations, the slide rule can quickly calculate specifications required for designing the pneumatic pressure control system.
Heretofore, it has been customary to select pneumatic devices according to approximate simple calculations on the slide rule because accurate dynamic simulations of a desired pneumatic pressure control system have not been possible. Therefore, the results of a conventional process of selecting pneumatic devices satisfy required values with considerably low probability, making it impossible to construct a desired pneumatic pressure control system of a minimum group of pneumatic devices and to achieve a minimum energy consumption and a minimum cost.
For the above reasons, there has been a demand for a process of quickly selecting a group of optimum pneumatic devices which satisfy conditions specified by the user, using highly accurate and reliable calculating methods. For selecting a pneumatic device, it is necessary to satisfy (1) a load condition (a dynamic condition for a selected system to operate sufficiently under input conditions, such as a load mass and thrust, an application, and a supplied air pressure, of a specified operating unit (pneumatic actuator)), (2) a velocity condition (a condition for a selected system to reach a stroke end of an output member (e.g., the piston of a cylinder) of a pneumatic actuator within a specified full stroke time), (3) a strength condition (a condition for a selected system to satisfy the specified load condition while preventing the pneumatic actuator from being buckled, deformed, or broken), and (4) a connecting condition (a condition for devices making a selected system to be connected normally).
The applicant of the present application has proposed a method of selecting a pneumatic device in order to satisfy the above conditions (e.g., see Japanese laid-open patent publication No. 2000-179503). The proposed method is advantageous in that it can select a pneumatic device highly accurately by using a dynamic characteristic analyzing process, unlike a conventional effective cross-sectional area method.
Usually, moisture condensation in a cylinder operating system refers to moisture condensation which is caused by compressed air adjusted in humidity while the cylinder is in operation. The moisture condensation occurs in two different phenomena, i.e., internal moisture condensation and external moisture condensation. The internal moisture condensation is a phenomenon in which humidity in the air is condensed within pneumatic devices or tubes due to a drop in the temperature of the air. The external moisture condensation is a phenomenon in which the air at a low temperature cools pneumatic devices which it contacts, condensing humidity contained in the air on outer surfaces of the pneumatic devices.
It is generally known that moisture condensation is basically caused by a reduction in the temperature of the air due to an adiabatic change of the air. In addition to the different phenomena of internal moisture condensation and external moisture condensation, the moisture condensation also occurs as moisture condensation on smaller-size cylinders and moisture condensation on larger-size cylinders.
It has been customary in the art to consider only a supply pressure, the size of a cylinder, and the size of a tube connected to the cylinder as elements that are involved in moisture condensation. Specifically, the volume of the tube is selected to be smaller than the volume of the cylinder for sufficiently mixing the remaining air in the cylinder and the tube with supplied fresh air and discharging the remaining air. Generally, the volumes of the cylinder and the tube are selected to satisfy the following formula:Volume of the air in the cylinder as converted under the atmospheric pressure×0.7≧internal volume of the tube
As shown in FIG. 21 of the accompanying drawings, it is judged that moisture condensation will take place if the volume ratio is smaller than 1/0.7, and no moisture condensation will take place if the volume ratio is greater than 1/0.7.
The above formula takes into account only the supply pressure, the size of the cylinder, and the size of the tube.
Since it has been the conventional practice to determine whether moisture condensation will occur or not solely based on the volume ratio of 1/0.7, moisture condensation may possibly be expected to occur even if it will not actually take place.
Accordingly, the user needs to determine whether moisture condensation will occur or not based on their experience after predictions have been made based on the above formula.
Generally, when the user selects a shock absorber to be used, the user establishes physical equations depending on the style of the impact that is expected, determines an impact velocity and a thrust force according to the physical equations, determines kinetic energy, thrust energy, and absorption energy based on the impact velocity and the thrust force, calculates an impact object equivalent mass from the absorption energy, compares the calculated impact object equivalent mass with an impact object equivalent mass calculated from data inherent in each candidate device, and determines whether the impact object equivalent mass is in an allowable range or not, and selects a shock absorber based on the decision.
According to the above process, the various data need to be calculated again when the style of the impact and conditions in use of a shock absorber are changed even slightly.
Since the data have to be determined based on complex and cumbersome calculations, it takes a long period of time to select a shock absorber. Sometimes, the user has relied on empirical selection of shock absorbers in order to avoid the above tedious and time-consuming selecting procedure.